Dual SIM in Samsung Galaxy 12 Android phone in US

[TomTaus_2129343]

I am going to New York and will very often be in WiFi zones.  I have a dual SIM slot Samsung Galaxy 12 Android phone and plan to by a local SIM card for texts and calls and data in the US. (The phone won't take an e-SIM)  I would still like to be able to use WhatsApp which, I think, is linked to my UK phone number and (I think?) through my Smarty SIM (?). I am not very techy and am not sure about this.

I don't plan to use the Smarty SIM while I am in the US.  Do I have to totally turn off my Smarty SIM to avoid charges?  Or is it enough if I turn off "data usage" on my Smarty SIM as I arrive in New York and only use the Smarty SIM when am in a WiFi area to access WhatsApp without being charged by Smarty?   

If I just turned off "data usage" but left my Smarty SIM on and received texts from the UK, would I be charged? If so, do I have to buy some sort of package in advance?

Any suggestions or explanations or advice gratefully received.

[MSF · Accepted solution]

@TomTaus_2129343 If you do not have any credit on your account then there cannot be any charges to your account.

To receive a text there is no charge. However, if you turn off your Smarty sim, you won't be able to receive any texts on that number either. I don't know anything much about Android, but can you turn off data in your settings? If you leave the Smarty sim on but turn mobile data off on that sim, I think you should be fine.

Also, if you accidentally try to use a service that requires payment, but have no credit, you simply won't be able to do it.